1. Field of the Invention
The present invention generally relates to enhancement of blood and lymph flow in a limb and the prevention of Deep Vein Thrombosis (DVT). More specifically, the present invention relates to a portable, self contained, mechanical device for enhancing the blood in a limb, enhancing the lymph and venous return from a limb, specifically a lower limb, towards the heart, aiming at reducing the risk of DVT formation, edema formation and improving the general circulation in a limb during periods of immobility.
2. Discussion of the Related Art
The development of a “blood clot” or Deep Vein Thrombosis (DVT) in a limb, specifically in the lower limbs, is a major health hazard. It may lead to local symptoms and signs such as redness, pain and swelling of the affected limb. It may also be a life hazard by sending small parts of a blood clot towards the lungs corking the circulation through the lungs (called Pulmonary Embolism), leading to reduced ability of the lungs and sometimes of the heart to function. This is accompanied by pain, shortness of breath, increased heart rate and other clinical signs and symptoms.
The development of DVT is believed to be related pathologically to Virchow's triad. More specifically, a DVT has increased incidence if three conditions are met in the vasculature; Stasis (reduced blood flow), Hypercouagulability (increased tendency of clotting in a blood vessel during normal conditions) and Endothelial damage (damage to the internal layer of the blood vessel promotes clot formation).
In the ambulatory person the muscles of the leg compress the deep venous system of the leg pushing the blood towards the heart. This phenomena is called the “muscle pump”. The muscles of the calf are traditionally implicated in the mechanism of the “muscle pump”.
During period of immobilization, stasis is believed to be the major risk factor for the formation of DVT. Immobilization includes any period of lack of physical activity whether in the supine or sitting position e.g. bed or chair ridden persons, during long automobile trips, long flights, long working hours in the sitting position etc.
Recently the medical community named the formation of DVT during long journeys, the “travelers thrombosis”. It is believed that around 5% of manifested DVT originate during traveling. This is believed to occur due to the prolonged immobilization, especially while in the sitting position. This position further compromises blood flow due to kinking of veins in the limb during the sitting position. It was further shown that enhancing the venous blood flow (via a compressing device) during flight, reduced discomfort, limb swelling, fatigue and aching when used on flight attendants.
Limb swelling and discomfort may be present also in states of lymph stasis such as after a mastectomy and in other conditions in which lymphatic return to the heart is impaired.
Increasing the flow of blood in the limb during periods of immobility is already a proven method to prevent the formation of DVT in the limb. It secondarily prevents the formation of pulmonary embolism (PE) that commonly originates from a DVT. Increasing the venous return from the lower limb can also prevent formation of edema, pain and discomfort in the limb during periods of immobilization.
Prevention of DVT related to stasis is commonly achieved via large and cumbersome devices. Most of these devices can be used only by trained medical staff. Such devices operate by either of two methods: Pneumatic/Hydraulic intermittent compressions or by direct intermittent electrical stimulation of the “muscle pump”. The Pneumatic/hydraulic devices use a sleeve or cuff with a bladder that is inflated and deflated by air or fluid compressor thus causing stimulation of the physiological “muscle pump”. The pneumatic/hydraulic devices usually require a sophisticated set of tubes and valves, a compressor, a source of fluid and a sophisticated computer control. Moreover such devices emit substantial noise while operating. The electrical stimulators work by delivering electrical impulses to the calf muscles. These devices require a sophisticated electronic apparatus and may be painful or irritating to patient.
Most existing devices aimed at preventing DVT are designed for use in the medical setting, by trained personal. Such devices are generally non-portable.
Accordingly it is the object of the present invention to provide a device for the enhancement of blood and lymph flow in a limb and the prevention of DVT development during periods of immobility which simulate intermittent muscle compression of a limb and is portable, self-contained, does not relay on, but is compatible with, external power source, and is easily carried, small, and lightweight.
It is a further object of the present invention to provide such a device which is simple to operate by a lay person without any special training in the field of medicine, is easily strapped over or attached to a limb and can be easily be adjusted to fit persons of any size.
Another object of the present invention is to provide such a device for the prevention of DVT which does not involve air compression and which operates silently, thus allows its operation in a populated closed space, such as during a flight, without causing any environmental noise annoyance.
Yet it is another object of the present invention is to provide the intermittent muscle compression by mechanical means, more specifically by transforming energy, electrical or magnetic, into mechanical activity via a system of rods and wheels.
A further object of the present invention is to provide such a device for the prevention of DVT that is easy to manufacture and is low cost.